Modeling Daily Wind Speed and Direction Using Harmonic Analysis for the Design of Seawater Greenhouse Prototype, in Kadzuhoni Kilifi County, Kenya

Abstract

The seawater greenhouse technology utilizes the radiation from the sun, seawater, humidity, wind speed and direction, and temperature to produce freshwater and cooled air in addition to providing the water for hydroponic section, supplying more sustainable environmental conditions for the cultivation of crops in arid and semi-arid coastal locations. The objective of the study was to examine the wind speed and its direction in the proposed Kadzuhoni area of Kilifi County for the design of a seawater greenhouse prototype, as well as to model wind speed and direction for the appropriate orientation of the seawater greenhouse prototype. Time series of wind speed and direction data were collected from the Kenya Meteorological Department (KMD) from 1st January 2021 to 31st December 2021. Statistical analysis was undertaken to model the wind speed and direction as well as perform the harmonic analysis model. The results showed that the wind speed in Kilifi County at Kadzuhoni proposed area for the seawater greenhouse prototype setup was found to vary with months. The general high wind speed recorded was 14 m/s and it was between May- June, and July – August, while the minimum wind speed was 2m/s and was found to be between December and January. For the East-West wind speed, it was observed that the maximum wind speed which was 11.22 m/s and blew from the East to the West, while the minimum wind speed was 10.79 m/s and blew from West to East. For the South-North wind speed, the maximum wind speed was 13.47 m/s and blew from the South to the North, while the minimum wind speed was 11.35 m/s and blew from North to South. In general, the calm wind has a frequency distribution of 11.8%, the speed 2.10 - 3.60 m/s has a frequency distribution of 4.9%, the speed 3.60 - 5.70 m/s has a frequency distribution of 12.3%, the speed 5.70 - 8.80 m/s has a frequency distribution of 25.3%, the speed 8.80-11.1 m/s has a frequency distribution of 14.8%, while the speed above 11.1 m/s has a frequency distribution of 30.8%. The harmonic analysis results of the model for observed and predicted were used to validate the model, by using the observed, predicted, and residual wind speed. It was found that there was no significant difference between the observed and the predicted values which characterized the model used as a good model. Since the southerly winds dominated with maximum speed of 13.47m/s, it is therefore recommended that the orientation of the seawater greenhouse, specifically the front evaporative pad, face the direction with the dominant wind speed for optimum collection of hot dry wind, and for cooling purposes. Therefore, these results will assist in setting up the seawater greenhouse prototype in Kadzuhoni proposed area without the use of fans.